NATS¶

Introduction¶

The Testcontainers module for NATS.

Adding this module to your project dependencies¶

Please run the following command to add the NATS module to your Go dependencies:

go get github.com/testcontainers/testcontainers-go/modules/nats

Usage example¶

Creating a NATS container

ctx := context.Background()

natsContainer, err := nats.Run(ctx, "nats:2.9")
defer func() {
    if err := testcontainers.TerminateContainer(natsContainer); err != nil {
        log.Printf("failed to terminate container: %s", err)
    }
}()
if err != nil {
    log.Printf("failed to start container: %s", err)
    return
}

Module Reference¶

Run function¶

Since v0.32.0

Info

The RunContainer(ctx, opts...) function is deprecated and will be removed in the next major release of Testcontainers for Go.

The NATS module exposes one entrypoint function to create the NATS container, and this function receives three parameters:

func Run(ctx context.Context, img string, opts ...testcontainers.ContainerCustomizer) (*NATSContainer, error)

context.Context, the Go context.
string, the Docker image to use.
testcontainers.ContainerCustomizer, a variadic argument for passing options.

Image¶

Use the second argument in the Run function to set a valid Docker image. In example: Run(context.Background(), "nats:2.9").

Container Options¶

When starting the NATS container, you can pass options in a variadic way to configure it.

Set username and password¶

Since v0.24.0

If you need to set different credentials, you can use WithUsername and WithPassword options. By default, the username, the password are not set. To establish the connection with the NATS container:

Connect using the credentials

ctx := context.Background()

ctr, err := nats.Run(ctx, "nats:2.9", nats.WithUsername("foo"), nats.WithPassword("bar"))
defer func() {
    if err := testcontainers.TerminateContainer(ctr); err != nil {
        log.Printf("failed to terminate container: %s", err)
    }
}()
if err != nil {
    log.Printf("failed to start container: %s", err)
    return
}

uri, err := ctr.ConnectionString(ctx)
if err != nil {
    log.Printf("failed to get connection string: %s", err)
    return
}

nc, err := natsgo.Connect(uri, natsgo.UserInfo(ctr.User, ctr.Password))
if err != nil {
    log.Printf("failed to connect to NATS: %s", err)
    return
}
defer nc.Close()

Cmd Arguments¶

Since v0.24.0

It's possible to pass extra arguments to the NATS container using the testcontainers.WithArgument option. E.g. nats.WithArgument("cluster_name", "c1"). These arguments are passed to the NATS server when it starts, as part of the command line arguments of the entrypoint.

Note

Arguments do not need to be prefixed with --: the NATS container will add them automatically.

Passing arguments

natsContainer1, err := nats.Run(ctx,
    "nats:2.9",
    network.WithNetwork([]string{"nats1"}, nwr),
    nats.WithArgument("name", "nats1"),
    nats.WithArgument("cluster_name", "c1"),
    nats.WithArgument("cluster", "nats://nats1:6222"),
    nats.WithArgument("routes", "nats://nats1:6222,nats://nats2:6222,nats://nats3:6222"),
    nats.WithArgument("http_port", "8222"),
)

Custom configuration file¶

Since v0.35.0

It's possible to pass a custom config file to NATS container using nats.WithConfigFile(strings.NewReader(config)). The content of io.Reader is passed as a -config /etc/nats.conf arguments to an entrypoint.

Note

Changing the connectivity (listen address or ports) can break the container setup. So configuration must be done with care.

The following options are exposed by the testcontainers package.

Basic Options¶

WithExposedPorts Since v0.37.0
WithEnv Since v0.29.0
WithWaitStrategy Since v0.20.0
WithAdditionalWaitStrategy Not available until the next release main
WithWaitStrategyAndDeadline Since v0.20.0
WithAdditionalWaitStrategyAndDeadline Not available until the next release main
WithEntrypoint Since v0.37.0
WithEntrypointArgs Since v0.37.0
WithCmd Since v0.37.0
WithCmdArgs Since v0.37.0
WithLabels Since v0.37.0

Lifecycle Options¶

WithLifecycleHooks Not available until the next release main
WithAdditionalLifecycleHooks Not available until the next release main
WithStartupCommand Since v0.25.0
WithAfterReadyCommand Since v0.28.0

Files & Mounts Options¶

Build Options¶

WithDockerfile Since v0.37.0

Logging Options¶

WithLogConsumers Since v0.28.0
WithLogConsumerConfig Not available until the next release main
WithLogger Since v0.29.0

Image Options¶

WithAlwaysPull Not available until the next release main
WithImageSubstitutors Since v0.26.0
WithImagePlatform Not available until the next release main

Networking Options¶

WithNetwork Since v0.27.0
WithNetworkByName Not available until the next release main
WithBridgeNetwork Not available until the next release main
WithNewNetwork Since v0.27.0

Advanced Options¶

WithHostPortAccess Since v0.31.0
WithConfigModifier Since v0.20.0
WithHostConfigModifier Since v0.20.0
WithEndpointSettingsModifier Since v0.20.0
CustomizeRequest Since v0.20.0
WithName Not available until the next release main
WithNoStart Not available until the next release main

Experimental Options¶

WithReuseByName Since v0.37.0

Container Methods¶

The NATS container exposes the following methods:

ConnectionString¶

Since v0.24.0

This method returns the connection string to connect to the NATS container, using the default 4222 port.

Get connection string

uri, err := ctr.ConnectionString(ctx)

MustConnectionString¶

Since v0.30.0

Exactly like ConnectionString, but it panics if an error occurs, returning just a string.

Examples¶

NATS Cluster¶

NATS Cluster

ctx := context.Background()

nwr, err := network.New(ctx)
if err != nil {
    log.Printf("failed to create network: %s", err)
    return
}

defer func() {
    if err := nwr.Remove(context.Background()); err != nil {
        log.Printf("failed to remove network: %s", err)
    }
}()

// withArguments {
natsContainer1, err := nats.Run(ctx,
    "nats:2.9",
    network.WithNetwork([]string{"nats1"}, nwr),
    nats.WithArgument("name", "nats1"),
    nats.WithArgument("cluster_name", "c1"),
    nats.WithArgument("cluster", "nats://nats1:6222"),
    nats.WithArgument("routes", "nats://nats1:6222,nats://nats2:6222,nats://nats3:6222"),
    nats.WithArgument("http_port", "8222"),
)
// }
defer func() {
    if err := testcontainers.TerminateContainer(natsContainer1); err != nil {
        log.Printf("failed to terminate container: %s", err)
    }
}()
if err != nil {
    log.Printf("failed to start container: %s", err)
    return
}

natsContainer2, err := nats.Run(ctx,
    "nats:2.9",
    network.WithNetwork([]string{"nats2"}, nwr),
    nats.WithArgument("name", "nats2"),
    nats.WithArgument("cluster_name", "c1"),
    nats.WithArgument("cluster", "nats://nats2:6222"),
    nats.WithArgument("routes", "nats://nats1:6222,nats://nats2:6222,nats://nats3:6222"),
    nats.WithArgument("http_port", "8222"),
)
defer func() {
    if err := testcontainers.TerminateContainer(natsContainer2); err != nil {
        log.Printf("failed to terminate container: %s", err)
    }
}()
if err != nil {
    log.Printf("failed to start container: %s", err)
    return
}

natsContainer3, err := nats.Run(ctx,
    "nats:2.9",
    network.WithNetwork([]string{"nats3"}, nwr),
    nats.WithArgument("name", "nats3"),
    nats.WithArgument("cluster_name", "c1"),
    nats.WithArgument("cluster", "nats://nats3:6222"),
    nats.WithArgument("routes", "nats://nats1:6222,nats://nats2:6222,nats://nats3:6222"),
    nats.WithArgument("http_port", "8222"),
)
defer func() {
    if err := testcontainers.TerminateContainer(natsContainer3); err != nil {
        log.Printf("failed to terminate container: %s", err)
    }
}()
if err != nil {
    log.Printf("failed to start container: %s", err)
    return
}

// cluster URL
servers := natsContainer1.MustConnectionString(ctx) + "," + natsContainer2.MustConnectionString(ctx) + "," + natsContainer3.MustConnectionString(ctx)

nc, err := natsgo.Connect(servers, natsgo.MaxReconnects(5), natsgo.ReconnectWait(2*time.Second))
if err != nil {
    log.Printf("connecting to nats container failed:\n\t%v\n", err)
    return
}

// Close connection
defer nc.Close()

{
    // Simple Publisher
    err = nc.Publish("foo", []byte("Hello World"))
    if err != nil {
        log.Printf("failed to publish message: %s", err)
        return
    }
}

{
    // Channel subscriber
    ch := make(chan *natsgo.Msg, 64)
    sub, err := nc.ChanSubscribe("channel", ch)
    if err != nil {
        log.Printf("failed to subscribe to message: %s", err)
        return
    }

    // Request
    err = nc.Publish("channel", []byte("Hello NATS Cluster!"))
    if err != nil {
        log.Printf("failed to publish message: %s", err)
        return
    }

    msg := <-ch
    fmt.Println(string(msg.Data))

    err = sub.Unsubscribe()
    if err != nil {
        log.Printf("failed to unsubscribe: %s", err)
        return
    }

    err = sub.Drain()
    if err != nil {
        log.Printf("failed to drain: %s", err)
        return
    }
}

{
    // Responding to a request message
    sub, err := nc.Subscribe("request", func(m *natsgo.Msg) {
        err1 := m.Respond([]byte("answer is 42"))
        if err1 != nil {
            log.Printf("failed to respond to message: %s", err1)
            return
        }
    })
    if err != nil {
        log.Printf("failed to subscribe to message: %s", err)
        return
    }

    // Request
    msg, err := nc.Request("request", []byte("what is the answer?"), 1*time.Second)
    if err != nil {
        log.Printf("failed to send request: %s", err)
        return
    }

    fmt.Println(string(msg.Data))

    err = sub.Unsubscribe()
    if err != nil {
        log.Printf("failed to unsubscribe: %s", err)
        return
    }

    err = sub.Drain()
    if err != nil {
        log.Printf("failed to drain: %s", err)
        return
    }
}

// Drain connection (Preferred for responders)
// Close() not needed if this is called.
err = nc.Drain()
if err != nil {
    log.Printf("failed to drain connection: %s", err)
    return
}

// Output:
// Hello NATS Cluster!
// answer is 42